Figure 1

Typical ARPES spectra for (a),(b) ${\mathrm{CDW}}^{0\mathrm{K}}$ at $T=15\mathrm{K}$ and (c),(d) ${\mathrm{CDW}}^{65\mathrm{K}}$ at $T=95\mathrm{K}$, respectively, at equal angle spacing along the marked cuts in the Brillouin zone in (f),(g). (e) Comparison of photoemission spectra for different $2H\mathrm{\text{−}}{\mathrm{Na}}_x{\mathrm{TaS}}_2$’s at high symmetry points $\mathbf{M}$ [also in (i)], $\Gamma$, $\mathbf{K}$, and at the Fermi crossing of cut 1. (f),(g) The photoemission intensity integrated within 10 meV of $E_{\mathrm{F}}$ is shown for ${\mathrm{CDW}}^{0\mathrm{K}}$ and ${\mathrm{CDW}}^{65\mathrm{K}}$, respectively. (Both data were taken at 15 K and the image was sixfold symmetrized.) The Fermi surfaces are marked by dashed lines, where the antibonding and bonding bands could be resolved for the $\Gamma$ pockets in the momentum distribution curve [one example is shown in (h) for ${\mathrm{CDW}}^{0\mathrm{K}}$].Reuse & Permissions

Figure 2

The CDW gap measurements of $2H\mathrm{\text{−}}{\mathrm{Na}}_x{\mathrm{TaS}}_2$. ARPES spectra taken at $\mathbf{M}$ for different temperatures for (a) ${\mathrm{CDW}}^{65\mathrm{K}}$ and (b) ${\mathrm{CDW}}^{0\mathrm{K}}$. (c),(d) The spectra in (a),(b) divided by the resolution convoluted Fermi-Dirac distribution at the corresponding temperatures. (e) The temperature dependence of the CDW gap. The solid line is the fit to a mean field formula, ${\Delta }_0\sqrt{1-(T/T_{\mathrm{CDW}})}$.Reuse & Permissions

Figure 3

(a) The false color plots of the CDW gap (upper half), and the spectral weight suppression ratio map (lower half, see text for explanation) in the first Brillouin zone of ${\mathrm{CDW}}^{65\mathrm{K}}$, where the dashed lines indicate the Fermi surfaces. States in the gapped region could be connected by the CDW wave vectors, ${\mathbf{Q}}_i$ ($i=1$, 2, 3), as indicated by the double-headed arrows. (b)–(d) comparison of the typical spectra in normal and CDW states at various momenta marked by the circled letters in (a). The spectra on the right have been divided by resolution convoluted Fermi-Dirac functions at corresponding temperatures.Reuse & Permissions

Figure 4

(a) Autocorrelation of the ARPES intensity at $E_{\mathrm{F}}$ in the normal state of ${\mathrm{CDW}}^{65\mathrm{K}}$ for wave vector along the $\Gamma \mathrm{\text{−}}\mathbf{M}$ direction. The dashed line is an exponential decay plus a constant, which is deducted in (b) to highlight the structure. (c) The partial autocorrelation in the 2D momentum transfer space obtained in the same way as in (b). Repeated zone scheme is taken in the integration, and thus $C(\overrightarrow{q},0)$ is symmetric with respect to the boundaries (white hexagon).Reuse & Permissions